🪴 Garden Soil & Mulch Volume Calculator
Enter your garden bed dimensions to calculate how much soil or mulch you'll need, in both cubic feet and cubic yards (the units most suppliers sell by).
Feet, yards and bags
Depth is entered in inches and everything else in feet, so the depth is divided by 12 before the three are multiplied:
cubic feet = length × width × (depth ÷ 12)
cubic yards = cubic feet ÷ 27
bags = cubic feet ÷ 2, rounded upA 10 ft × 4 ft bed mulched 3 inches deep is 40 sq ft × 0.25 ft = 10 cubic feet. That is 0.37 cubic yards, or 5 of the standard 2 cubic foot bags. Bags always round up, since suppliers do not sell fractions of one.
Ordering the right amount
- One cubic yard covers 108 square feet at 3 inches, 162 sq ft at 2 inches, or 81 sq ft at 4 inches. Bulk is normally cheaper than bags beyond about two yards, and 27 bags make a yard.
- Order a little over. Loose bark and compost settle by something like a tenth once they are spread and rained on, and beds are rarely the exact rectangle you measured.
- Check the weight before hauling it yourself. A cubic yard of wood mulch is roughly 400–800 lb depending on how wet it is; topsoil or compost is nearer a ton, past what many car boots and trailers are rated for.
Frequently asked questions
How many bags of mulch in a cubic yard?
Thirteen and a half 2 cubic foot bags, so 14 in practice, or 27 of the 1 cubic foot size. Past a couple of yards, bulk delivery is usually cheaper.
How deep should mulch be?
Two to four inches over open soil is the usual advice — enough to block light from weed seeds without smothering roots. Keep it pulled back from trunks and stems, where piled mulch holds moisture against the bark and invites rot.
How much soil do I need for a 4x8 raised bed?
At 10 inches deep, 4 × 8 × 0.833 = 26.7 cubic feet, just under a cubic yard. Fill it to the brim and expect the level to drop over the first season as the organic matter breaks down.